Driveways, Walkways Alligator cracks in driveway

Published on February 17th, 2017 | by Henri


Cracks in asphalt driveway

Q.  I am located in Shelburne, Vermont and I have an interesting phenomenon that takes place during the winter and spring months. I have an asphalt driveway that is about 10 years old. I have sealed it a couple times, probably more than you would recommend. During sunny days, there are two different spots in the driveway that will start “weeping” water for about an hour. I assume that the angle of the sloped driveway with the heat of the sun is melting the frost. I do have “alligator” cracks throughout the whole driveway and not an extraordinary amount in those particular spots. I am concerned that this constant freeze/thaw cycle will start causing an increased amount of cracks or possible heaves. Should I continue to seal the driveway, possibly preventing the water from escaping?

A.  There are many reasons for alligator cracks to develop; too many to discuss here. It is possible that the driveway was sealed too soon, before the asphalt had sufficiently cured (two to three years until the asphalt turns grey), and that the sealer was applied too thickly. It is also possible that the subsequent coats were applied before the previous coat had worn off enough. The resulting build-up may be responsible.

Another possibility, if the alligator cracks are longitudinal and located along vehicle traffic, they may be caused by weak asphalt unable to support the weight. However, this is mostly found on roads and not on driveways. It they are found throughout the driveway, the cause may be as discussed above, or a weak mix or faulty installation.

The interesting “weeping” may be caused by snowmelt or rain having penetrated through the alligator cracks, freezing and subsequently thawing on sunny days as the dark asphalt heats up. It’s hard to tell for sure. But if it is the cause of the weeping, resealing with a coal tar or acrylic polymer sealer should help seal the alligator cracks unless they are too big and beyond repair. But if the existing coats of sealer are too thick as it is, applying a new coat may not help and may add to the problem.

Coal tar sealers are generally considered the best, but are not good for the environment because of the high VOC they exude. Acrylic polymer sealers are just as good, albeit considerably more expensive,  while emitting far less VOC.

It may be a good idea for you to have an experienced asphalt contractor look your driveway over to advise you. He or she may recommend one of the repair products available, the application of a high-quality sealer or laying a thin layer of new asphalt over the existing one.

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